Running Average Cache Hit Rate

1. A method comprising: calculating a cache hit rate for a cache; determining a difference between the cache hit rate and an average cache hit rate for the cache that corresponds to an average of historical cache hit rates; updating a cumulative delta value by adding the difference to the cumulative delta value, wherein the cumulative delta value corresponds to an accumulation of delta values between successive cache hit rates and the average cache hit rate; determining that the updated cumulative delta value exceeds a delta range; updating, in response to determining that the updated cumulative delta value exceeds the delta range, the average cache hit rate; resetting the cumulative delta value in response to updating the average cache hit rate; and updating a cache allocation policy for the cache based on the updated average cache hit rate.

2. The method of claim 1, wherein: determining that the updated cumulative delta value exceeds the delta range includes determining that the updated cumulative delta value exceeds an upper delta threshold; updating the average cache hit rate includes updating, in response to the updated cumulative delta value exceeding the upper delta threshold, the average cache hit rate by incrementing the average cache hit rate using an increment factor that is based on a magnitude of the updated cumulative delta value exceeding the upper delta threshold; determining that the updated cumulative delta value exceeds the delta range includes determining that the updated cumulative delta value exceeds the delta range by determining that the updated cumulative delta value is below a lower delta threshold; updating the average cache hit rate includes updating, in response to the updated cumulative delta value being below the lower delta threshold, the average cache hit rate by decrementing the average cache hit rate using a decrement factor that is based on a magnitude of the updated cumulative delta value being below the lower delta threshold; and resetting the cumulative delta value includes resetting the cumulative delta value using the updated average cache hit rate.

3. A device comprising: a first register configured to store a cumulative delta value, wherein the cumulative delta value corresponds to an accumulation of delta values between successive cache hit rates and an average cache hit rate that corresponds to an average of historical cache hit rates; a second register configured to store the average cache hit rate; and a control circuit configured to: calculate a cache hit rate; update the cumulative delta value based on the cache hit rate and the average cache hit rate; update the average cache hit rate based on the updated cumulative delta value; and update a cache allocation policy based on the updated average cache hit rate.

4. The device of claim 3, wherein the control circuit is configured to update the cumulative delta value by: determining a difference between the cache hit rate and the average cache hit rate; and adding the difference to the cumulative delta value.

5. The device of claim 3, wherein the control circuit is configured to update the average cache hit rate based on determining that the updated cumulative delta value exceeds a delta range.

6. The device of claim 5, wherein the control circuit is configured to determine that the updated cumulative delta value exceeds the delta range by determining that the updated cumulative delta value exceeds an upper delta threshold.

7. The device of claim 6, wherein the control circuit is configured to update the average cache hit rate by incrementing the average cache hit rate in response to the updated cumulative delta value exceeding the upper delta threshold.

8. The device of claim 7, wherein the control circuit is configured to increment the average cache hit rate using an increment factor.

9. The device of claim 8, wherein the increment factor is based on a magnitude of the updated cumulative delta value exceeding the upper delta threshold.

10. The device of claim 5, wherein the control circuit is configured to determine that the updated cumulative delta value exceeds the delta range by determining that the updated cumulative delta value is below a lower delta threshold.

11. The device of claim 10, wherein the control circuit is configured to update the average cache hit rate by decrementing the average cache hit rate in response to the updated cumulative delta value being below the lower delta threshold.

12. The device of claim 11, wherein the control circuit is configured to decrement the average cache hit rate using a decrement factor.

13. The device of claim 12, wherein the decrement factor is based on a magnitude of the updated cumulative delta value being below the lower delta threshold.

14. The device of claim 3, wherein the control circuit is further configured to reset the cumulative delta value in response to updating the average cache hit rate.

15. The device of claim 14, wherein the control circuit is configured to reset the cumulative delta value using the updated average cache hit rate.

16. A system comprising: a physical memory; at least one physical processor comprising a cache; a first register configured to store a cumulative delta value, wherein the cumulative delta value corresponds to an accumulation of delta values between successive cache hit rates and an average cache hit rate that corresponds to an average of historical cache hit rates; a second register configured to store the average cache hit rate for the cache; and a control circuit configured to: calculate a cache hit rate for the cache; update, in the first register, the cumulative delta value based on the cache hit rate and the average cache hit rate; determine that the updated cumulative delta value exceeds a delta range; update, in response to determining that the updated cumulative delta value exceeds the delta range, the average cache hit rate in the second register; and update a cache allocation policy for the cache based on the updated average cache hit rate.

17. The system of claim 16, wherein the control circuit is configured to update the cumulative delta value by: determining a difference between the cache hit rate and the average cache hit rate; and adding the difference to the cumulative delta value.

18. The system of claim 16, wherein: the control circuit is configured to determine that the updated cumulative delta value exceeds the delta range by determining that the updated cumulative delta value exceeds an upper delta threshold; and the control circuit is configured to update, in response to the updated cumulative delta value exceeding the upper delta threshold, the average cache hit rate by incrementing the average cache hit rate using an increment factor that is based on a magnitude of the updated cumulative delta value exceeding the upper delta threshold.

19. The system of claim 16, wherein: the control circuit is configured to determine that the updated cumulative delta value exceeds the delta range by determining that the updated cumulative delta value is below a lower delta threshold; and the control circuit is configured to update, in response to the updated cumulative delta value being below the lower delta threshold, the average cache hit rate by decrementing the average cache hit rate using a decrement factor that is based on a magnitude of the updated cumulative delta value being below the lower delta threshold.

20. The system of claim 16, wherein the control circuit is further configured to reset the cumulative delta value using the updated average cache hit rate.